Abortion Control,
Vaccination, and
Prevention in the Ewe
Suelee Robbe, DVM
Veterinary Diagnostic and Production
Animal Medicine
Iowa State University
What is a Normal Abortion
Rate?
Less than 1%
ovine abortions
• Use the diagnostic laboratory
• Do not put aborted fetuses in the
freezer
• 60%-70% are diagnosed as infectious
causes of abortion.
• Toxoplasma, Chlamydia, and
Campylobacter are the 3 most common
causes.
Toxoplasma Abortions
• Ewes that are
not immune to
Toxoplasma
are exposed
during
pregnancy.
Cats eat tissue and
defecate in sheep
feed or feed bunks
Animals infected
with Toxo in tissue
Abortion
Large amounts of
infected tissue for cats
to eat.
Ewes
unknowingly
eat Toxo eggs
Prevention of Toxoplasma
Abortions
• *Avoid having a young/transient cat
population.
• Avoid having ewes eat where cats
frequent.
• Make feed storage areas cat proof
(tough to do).
• Maintain effective rodent control.
• Prevent cats from feeding on
sheep/lamb carcasses.
Vaccination against
Toxoplasma
• There is an effective vaccine in Europe.
• Feed ewe-lambs contaminated feed when
they are not pregnant.
• Once a ewe aborts (or exposed) she is
immune.
• Ionophores have been used… This is an
illegal use, only partially effective.
Questions???
Chlamydia Abortions
• Economically a very important disease for
sheep producers
• Abortion occurs in the last trimester
• Can be the cause of an abortion storm,
but not usually
• Lambs may also be carried full term, but
are born dead or weak.
• Can be a chronic continual problem with 15% of ewes aborting annually. (Typical)
Chlamydial Abortion
• Ewes can become infected during one
lambing season and abort the next
lambing season.
• A replacement ewe lamb infected at birth
can harbor the organism and abort her
lambs.
• Ewes carrying multiple fetuses are more
likely to abort
• There are flocks that are free of
Chlamydia. (Or at least the strain that
causes abortion.)
Purchased Ewes can bring
Chlamydia into a Clean Flock
Infected Ewe
How Chlamydia Perpetuates in a Flock
Lambs from these ewes can
be born infected (will be
carriers) and can abort their
first lambs
Infects naive ewes
Carrier Ewe
Many of these
ewes will abort
at next lambing
and become
carrier ewes
How Chlamydia Perpetuates in a Flock
(cont.)
Their offspring are infected and
some of them will abort at
subsequent lambings
Infected flock of
carrier ewes.
These ewes
don’t abort.
Chlamydia is
perpetuated in the
flock with mostly
ewe-lambs and
yearlings aborting
~1-5% rate annually.
Controlling Chlamydial
Abortion
• Use caution when selecting ewe lamb
replacements.
• Run ewe lambs separate from main flock.
• Lamb ewe lambs away from/ after main
flock.
• Immediately isolate aborting ewes;
consider culling them.
Controlling Chlamydial
Abortion
• Pick up afterbirths, dead fetuses and
throw barn lime down on the area if
appropriate.
• Do not feed on the ground in a dry lot
situation.
• Avoid crowding, have plenty of bunk
space.
• Tetracycline to help prevent shedding
Vaccination against Chlamydia
• Vaccines may decrease severity of initial
infection.
• Once a flock is infected, there is no
evidence vaccine has any impact if all
the studies are examined.
Questions???
Campylobacter Abortions
• Abortions occur in the last 6 weeks of
pregnancy.
• Lambs may be carried full term, but are
born dead or weak.
• Most common cause of abortion storms
with 5-50% aborting.
• Typically the disease is self-limiting. (unlike
Chlamydia)
Campylobacter Abortions
• Many sheep carry Campylobacter as normal
intestinal flora.
• Ewes ingest a new strain of
Campylobacter. If this happens after the
12th week of pregnancy or later, the ewe
very likely aborts.
• Infection is further spread by direct contact
with aborted fetus/membranes.
• Ewes that are not pregnant develop
immunity and will not abort subsequent
fetuses.
Preventing Campylobacter
Abortions
• Have ewes thoroughly mixed before
breeding.
• If you don’t have a closed ewe flock,
consider vaccinating.
• Do not feed on the ground in a dry lot
situation.
• Avoid crowding, have plenty of bunk
space.
Campylobacter Vaccination
• One of the poorest vaccines routinely
recommended by sheep health experts.
• At best 80% efficacy, probably closer to
0%.
• Efficacy depends on strain of
campylobacter.
• Don’t rely on vaccination in place of good
management.
Lamb/Sheep Quality
Assurance
Suelee Robbe, DVM
Veterinary diagnostic and Production
Animal Medicine
Iowa State University
Quality Assurance Programs
• Standardized methods of handling,
treating, and processing food animals to
help ensure quality and wholesomeness
to the consumer.
Where is the sheep industry
in this picture?
Goals of a Quality Assurance
program for Sheep
• Keep muscle damage down to a minimum.
(Injection sites, bruises, etc…)
• Eliminate illegal drug residues and foreign
objects.
• Prudent use of extra-label drugs.
• Consistent meat “eating quality”
• Wool QA.
Minimizing Injection Site
Damage
• Syringe handling and care
 Rinse after each use.
 Allow syringe to dry thoroughly.
 Do not use soap to clean. (unless NO MLV
products are used)
 Lube plungers with approved products.
Minimizing Injection Site
Damage
• Needle handling
– Stainless Steel, Disposable
– Different needle for drawing out of a multidose bottle.
– Change after bent, burred needles.
Needles (SQ)
• Acceptable needles
 18 gauge by ½ inch (5/8 inch in
disposable)
 20 gauge by ½ inch
• Acceptable areas
 Neck (preferred)
 Behind elbow
 Inside loose skin of the flank (Only on
lambs)
Needles (IM)
• (Avoid if possible)
– 16 gauge by ¾ inch
– 18 gauge by ¾ inch
– 20 gauge by ¾ inch
• Neck only!
QA Guidelines (cont.)
• Follow Label instructions.
• Never mix products in one injection.
• Never put more than 10 cc’s per site in
adult ewes, 5 cc’s in lambs, feeder
lambs.
• Know the Products you are using.
• Follow common sense.
Goals of a Quality Assurance
program for Sheep
• Keep muscle damage down to a minimum.
(Injection sites, bruises, etc…)
• Eliminate illegal drug residues and foreign
objects.
• Prudent use of extra-label drugs.
• Consistent meat “eating quality”
• Wool QA.
Eliminating Drug Residues
• Understand and adhere to withdrawal
times.
• Do not use drugs that are not approved
for use in sheep without veterinary
approval.
– This includes topical insecticides, over the
counter human remedies, etc…
What are the sheep Approved
Antibiotics?
• Erythromycin/ Gallimycin
– Unacceptable Tissue reactivity.
• Penicillin
– 3000 units per pound of body weight or 1.0 ml (cc)
for each 100 lbs. once daily.
• Naxcel (ceftiofur) (prescription use only)
– 0.5-1 mg/lb. IM (If reconstituted per label
directions, 1-2 cc/100 lbs.)
• If these drugs are used any way other than the label,
it must be done with veterinary approval.
When can we use Drugs that
are Not Approved for Sheep?
• This is addressed in a law that was passed
called AMDUCA (Animal Medicinal Drug Use
Clarification Act).
• This act gives veterinarians the right to use
and recommend the use of drugs that are not
approved for use in sheep.
(ONLY under certain circumstances)
AMDUCA
• A valid VCPR exists.
• The health of the animal is at immediate risk
and suffering or death would result if a drug
were not used.
• There is not an approved drug on the market
for that particular condition.
• Accurate records of usage are kept
• Treated animals can be easily identified for an
extended period.
• An extended withdrawal time is used to assure
that no illegal residue occurs.
AMDUCA (cont.)
• The veterinarian and producer accept full
responsibility for any illegal residue that
occurs.
Recommendations to
Producers for Prudent
Antibiotic Use
• Before treatment is given, a diagnosis must
be made by you, or your veterinarian.
• Use a sheep veterinarian that gives you
treatment protocols. (preferably written)
• Follow your sheep veterinarian’s advice and
give feedback.
• Every time you give an antibiotic understand
and adhere to the withdrawal time.
• Keep Appropriate Records
Veterinarians Role in the
Sheep Industry
• We must be able to justify ourselves
economically.
• Medicine on a Flock basis
– QA, Protocols, outbreak treatments,
diagnostic assistance.
• Prevention of Disease on a Flock basis.
– Biosecurity Protocols, Risk Assessments
Parasite Control Programs
Suelee Robbe, DVM, MS
Diagnostic and Production Animal Medicine,
Iowa State University
Typical parasitic lifestyle
Adults-Hang out in the GI tract
• Abomasum
– Haemonchus , Ostertagia, some
Trichostrongylus
• Small intestine
– Trichostrongylus, Nematodirus
• May live for longer than a year, but
usually egg production peaks ~ 3
months
Typical parasitic lifestyle
Eggs:
Development from egg to infective (L3)
larvae can occur as early as 6 days
Molt into L1’s in the egg then hatch
Nematodirus develop into L3’s in the egg,
then hatch
Most ova do not survive very cold
ambient temperatures
Typical parasitic lifestyle
• L3’s - infective stage
• Thick cuticle protects them from drying
– Cannot feed - finite life span
– Warm temperatures increase their
metabolic rate.
• Can survive some freezing
Typical parasitic lifestyle
• L3’s molt in to L4’s soon after their
ingestion where they may “rest for a
time”
• Hypobiosis
• occurs in most species of worms
Haemonchus
• Adults live in abomasum
– ingest 0.05ml blood/worm/day
– 5000 worms will remove 250 ml of blood.
• Adults are very prolific egg layers
• Haemonchus L3’s are not as cold hardy
as others
• Most L3’s live for 1-3 months
Others parasites
• Nematodirus
• Ostertagia
• Trichostrongylus
• Plan your parasite program to control
haemonchus
Coccidia
• All sheep shed coccidia
• Clinical signs
– Sudden death
– Scouring lambs
– weight loss
Prevention
• Keep environment clean and dry
• Design feed and water bunks so lambs
cannot step in them
• Feed coccidiostats
– Decox
– Bovatec
Treatment
• Amprolium
• Sulfa drugs
Parasite control
• Control of L3’s on pasture is critical, and
is related to number of adults in the
animal.
• A parasite program that:
Targets L3’s controls the parasite burdens
in grazing sheep.
Targets L4’s and adults in the animal does
not necessarily control L3’s on pasture.
Example Sheep flock
Remote Pasture
Moves here in
the summer.
Working
facility/barns
Close Pasture
Winter close up
pasture.
Example Sheep and goat flock
Remote Pasture
Flock here since
June 20
FEC Aug 1st.
Dewormed
Dectomax Sept 2
Working
facility/barns
Close Pasture
Wants to move
here Sept. 30
last sheep/goat
July 4th
Example Sheep and goat flock
Remote Pasture
Working
facility/barns
Close Pasture
L3 Burden in Oct?
L3 Burden in
Sept/Oct?
HIGH
LOW
Parasite control programs
• Development and survival of infective
larvae depend on temperature and
moisture.
• Optimums vary with worm species.
Parasite control
• Host Resistance depends on
– Age
– Vigor
– Genetic constitution
– Presence or absence of established
parasite infections
– Acquired immunity
Parasite control
• Maturation of 4th stage larvae in host
may be arrested.
Anthelmentics
Long acting
• ivermectin-larvicidal ~10 days
• doramectin -larvicidal ~20 days
• eprinomectin
• moxidectin
Pour-ons do not work in sheep
Disadvantages: Parasite resistance, cost,
WDT, Not Ovicidal
Anthelmentics
Short acting or purge
• levamisole
– relatively poor against immature or
arrested L4 larvae
– Low margin of safety
• benzimidazoles (fenbendazole,
oxfendazole, albendazole)
These products are ovicidal
Host resistance issues
• kids typically more susceptible
• goats producing more milk typically
have higher parasite burdens
• animals under stress/have pre-existing
conditions are more likely have higher
parasite burdens
Parasite Resistance
• The best way to avoid resistance to an
anthelmintic is not to use it.
• If you rely on just anthelmintics as your
sole parasite control program you WILL
get resistance.
• There never has been and most likely
never will be an anthelmintic that won’t
have resistance problems